With the increased use of antibodies as reagents in clinical diagnostics and cancer therapy, the need has arisen for purification of such antibodies. Conventional purification techniques, in which mixtures containing antibodies are passed through a suitable column to selectively adsorb the antibodies from the mixture and the adsorbed antibodies are later eluted from the column in purified form, have been used for this purpose. However, the yield and purity of the isolated antibodies which can be obtained is limited by the lack of specificity of the column.
Previous processes for the purification of immunoglobulins, for example, suffered from the relatively low capacity of adsorbents for the immunoglobulins. In one such process, various fractions of immunoglobulins from sera of different mammalian species were adsorbed upon protein A-Sepharose.RTM. adsorbents at pH 7 or higher and eluted at pH values ranging from pH 2.5 to pH 6.5 [R. Lindmark, K. Thoren-Tolling and J Sjoquist, "Binding of Immunoglobulins to Protein A and Immunoglobulin Levels in Mammalian Sera," Journal of Immunological Methods, 52:1 (1983)]. It was also known that binding of mouse IgG to protein A-Sepharose.RTM. is pH dependent and that optimum adsorption occurs using 0.1 M sodium phosphate, pH 8.0 buffer. [P.L. Ey, S.J. Prowse and C.R. Jenkin, "Isolation of Pure IgG.sub.1, IgG.sub.2a and IgG.sub.2b Immunoglobulins from Mouse Serum Using Protein A-Sepharose," Immunochemistry, 15:429 (1978)].
Recently, efforts have been made to increase the recovery of various immunoglobulins using specially formulated buffers. ["Mouse Monoclonal IgG.sub.1, Purification with Affi-Gel.sup.R Protein A," Bulletin 1172, Bio-Rad Laboratories, Bio-Rad Chemical Division, Richmond, Calif. (1984)]. A process for purifying immunoglobulins using inorganic salts at concentrations within certain ranges specified for particular pH values is described in U.S. Pat. No. 4,704,366. Another process for purifying immunoglobulins using a combination of monovalent cations and polybasic anions within a specified concentration range in a buffer is described in U.S. Pat. No. 4,801,867. It would nonetheless be desirable to provide a purification process which would result in still higher yields of immunoglobulins.
Accordingly, it is an object of the present invention to provide an improved process for the purification of antibodies.
It is another object of the present invention to provide such a process which does not require additional purification steps.
A further object of the present invention is to provide a rapid, convenient and economically practical process for improving the yield of antibodies recovered in such purification by such adsorption techniques.
Other objects and advantages of this invention will become apparent from the following detailed disclosure.